In the manufacturing of a product, the product is usually processed at many work stations or processing apparatus. A transporting of partially finished products is therefore conducted in a manufacturing process.
For example, to complete the fabrication of semiconductor wafers, various steps of deposition, cleaning, ion implantation, etching and passivation steps may be carried out before the semiconductor wafers are packaged for shipment. Each of these fabrication steps may be performed in different process machines, i.e. a chemical vapor deposition tool, an ion implantation tool, an etcher, etc. Therefore, the semiconductor wafers that are partially processed are transported between various work stations many times before the fabrication process is completed.
In some systems, cassette pods are used to store batches of the semiconductor wafers. To conduct the transporting of the semiconductor wafers, the semiconductor wafers are moved into the cassette pods, and the cassette pods and the semiconductor wafers are transported together by a handling and transport equipment. Operation of the handling and transport equipment may be conducted under automatic control using a programmed computer which issues control signals for operating the equipment with little or no intervention by an operator. Therefore the handling and transport equipment transports the cassette pods and the semiconductor wafers between two positions for different purposes.
Consequently, a safe transporting of the semiconductor wafers in a semiconductor fabrication system is desired.